On Mon, Jan 17, 2022 at 04:53:48AM +0200, Jarkko Sakkinen wrote:
> On Tue, Nov 30, 2021 at 08:15:36PM +0800, Yang Zhong wrote:
> > On Thu, Nov 25, 2021 at 08:47:22PM +0800, Yang Zhong wrote:
> > > Hello Paolo,
> > >
> > > Our customer used the Libvirt XML to start a SGX VM, but failed.
> > >
> > > libvirt.libvirtError: internal error: unable to execute QEMU command 'qom-get': Property 'sgx-epc.unavailable-features' not found
> > >
> > > The XML file,
> > > <qemu:commandline>
> > > <qemu:arg value="-cpu"/>
> > > <qemu:arg value="host,+sgx,+sgx-debug,+sgx-exinfo,+sgx-kss,+sgx-mode64,+sgx-provisionkey,+sgx-tokenkey,+sgx1,+sgx2,+sgxlc"/>
> > > <qemu:arg value="-object"/>
> > > <qemu:arg value="memory-backend-epc,id=mem1,size=16M,prealloc=on"/>
> > > <qemu:arg value="-M"/>
> > > <qemu:arg value="sgx-epc.0.memdev=mem1"/>
> > > </qemu:commandline>
> > >
> > > The new compound property command should be located in /machine path,
> > > which are different with old command '-sgx-epc id=epc1,memdev=mem1'.
> > >
> > > I also tried this from Qemu monitor tool,
> > > (qemu) qom-list /machine
> > > type (string)
> > > kernel (string)
> > > ......
> > > sgx-epc (SgxEPC)
> > > ......
> > > sgx-epc[0] (child<memory-region>)
> > > ......
> > >
> > > We can find sgx-epc from /machine list.
> > >
> >
> > This issue is clear now, which is caused by Libvirt to get the CPU's unavailable-features by below command:
> > {"execute":"qom-get","arguments":{"path":"/machine/unattached/device[0]","property":"unavailable-features"}
> >
> > but in SGX vm, since the sgx is initialized before VCPU because sgx need set the virtual EPC info in the cpuid.
> >
> > So the /machine/unattached/device[0] is occupied by sgx, which fail to get the unvailable-features from
> > /machine/unattached/device[0].
> >
> >
> > We need fix this issue, but this can be done in Qemu or Libvirt side.
> >
> > 1) Libvirt side
> > If the libvirt support SGX EPCs, libvirt can use /machine/unattached/device[n] to check "unavailable-features".
> > n is the next number of sgx's unattached_count.
> >
> > 2) Qemu side
> >
> > One temp patch to create one /sgx in the /machine in the device_set_realized()
> > diff --git a/hw/core/qdev.c b/hw/core/qdev.c
> > index 84f3019440..4154eef0d8 100644
> > --- a/hw/core/qdev.c
> > +++ b/hw/core/qdev.c
> > @@ -497,7 +497,7 @@ static void device_set_realized(Object *obj, bool value, Error **errp)
> > NamedClockList *ncl;
> > Error *local_err = NULL;
> > bool unattached_parent = false;
> > - static int unattached_count;
> > + static int unattached_count, sgx_count;
> >
> > if (dev->hotplugged && !dc->hotpluggable) {
> > error_setg(errp, QERR_DEVICE_NO_HOTPLUG, object_get_typename(obj));
> > @@ -509,7 +509,15 @@ static void device_set_realized(Object *obj, bool value, Error **errp)
> > goto fail;
> > }
> >
> > - if (!obj->parent) {
> > + if (!obj->parent && !strcmp(object_get_typename(obj), "sgx-epc")) {
> > + gchar *name = g_strdup_printf("device[%d]", sgx_count++);
> > +
> > + object_property_add_child(container_get(qdev_get_machine(),
> > + "/sgx"),
> > + name, obj);
> > + unattached_parent = true;
> > + g_free(name);
> > + } else if (!obj->parent) {
> > gchar *name = g_strdup_printf("device[%d]", unattached_count++);
> >
> > object_property_add_child(container_get(qdev_get_machine()
> >
> > This patch can make sure vcpu is still /machine/unattached/device[0].
> >
> >
> > Which solution is best? thanks!
>
> Has either of the fixes reached yet reached upstream or not?
I built qemu from git with the fix applied. It fixed the issue for me.
Tested-by: Jarkko Sakkinen <jarkko@xxxxxxxxxx>
> > Yang
BR, Jarkko
